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Actively exploited vulnerability

Citrix Workspace Application and Receiver for Windows: code execution flaw under attack

CVE-2019-11634 · Citrix Workspace Application and Receiver for Windows Remote Code Execution Vulnerability

Concerns everyone who uses it9.8 criticalUsed in ransomware attacks

What is affected

Citrix Workspace Application and Receiver for Windows is found on ordinary personal computers and phones, so this is not only a problem for companies. If you use it and have not updated since the fix was released, you are exposed.

Citrix Workspace Application and Receiver for Windows contains remote code execution vulnerability resulting from local drive access preferences not being enforced into the clients' local drives.

CISA's description

What an attacker can do

This is a code execution flaw. It lets an attacker run their own commands or programs on the affected system. In practice that usually means taking it over: installing malware, stealing data or using it to reach other devices on the same network.

How it is reached
Over the internet or network
Access the attacker needs
No account needed
Does the victim have to do something?
No, works without the victim doing anything

CISA records this vulnerability as known to be used in ransomware campaigns: attackers use it to get in, then encrypt files and demand payment.

What to do

  1. Update Citrix Workspace Application and Receiver for Windows now. Open the update or "About" screen, install whatever is offered and restart the app or device, because the fix is not active until you do.
  2. Turn on automatic updates so the next fix arrives without you having to look for it.
  3. If your device is too old to receive this update, stop using the affected app for anything sensitive and plan a replacement.

Apply updates per vendor instructions.

Action required by CISA for US federal agencies

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on November 3, 2021, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by May 3, 2022, a deadline that has already passed. That deadline does not bind anyone else, but it shows how seriously the agency rates it.

The EPSS model estimates a 8.1% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 95% of all scored vulnerabilities.

Its CVSS severity score is 9.8 out of 10 (critical), as recorded in the US National Vulnerability Database.

Technical description

Citrix Workspace App before 1904 for Windows has Incorrect Access Control.

NIST National Vulnerability Database
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